| abstract |
A rigid electrical heating element having a thin, rigid, electrically insulating, air-impervious layer and a thick, insulating polyurethane layer formed in situ connected to said rigid layer by a conducting film based upon a synthetic resin, electrically conducting particles and potassium silicate or sodium silicate. Electrodes and corresponding electrical connections are mounted on the film after it has been applied by deposition of an aqueous plastic dispersion of said resin particles and silicate material. The silicates being present in the heating film in sufficient quantity to protect the heating film from attack by the starting reaction components of the polyurethane layer. The rigid layer may be a synthetic resin panel having a decorative heat irradiating surface. |